1. Field of the Invention
The present invention relates generally motor control systems, and more specifically to a vehicle door control system that detects and responds to abnormal door operation.
2. Background of the Invention
Automatic vehicle door opening and closing mechanisms are in widespread use in public transportation systems such as trains and buses, as well as in private vehicles adapted for use by the handicapped. The control of the operation of a vehicle door is typically performed by an electronic control system that determines the position and speed of a moving element of an electric motor that operates the door positioning mechanism. The control system typically stops the electric motor when an abnormality is detected in the operation of the door positioning mechanism by observing position and speed signals from a position detector coupled to the motor and/or positioning mechanism. The control system responds to the detection of the abnormality by removing power from the electric motor in order to prevent breakage of the positioning mechanism, the vehicle door or damage to the electric motor.
Japan Patent Application JP-A-5-344775 discloses a vehicle door control system that provides a signal that is generated when abnormal position or speed of the positioning system is detected. The signal causes the servo motor to stop operating. Japan Patent Application JP-A-5-98867 discloses a vehicle door control system that restricts operation of an electric motor that moves a vehicle door for a predetermined time period when abnormal operation is detected. In both of the systems described in the above-referenced patent applications, the electric motor is ultimately stopped when abnormal operation is detected.
In addition to detecting abnormal door/door positioner operation, indications of continuous abnormal operation in the above-mentioned systems occur when a disconnection or failure of a feedback signal from the position detector occurs and indications of temporary abnormal operation occur when electrical noise is present on the position detector feedback signal(s), such noise due to electrical storms or electrical noise generated by operation of the electric motor. In either case, if the electric motor is controlled in position and speed in conformity with an erroneous feedback signal, the electric motor, positioning system and/or the vehicle door may be damaged. Therefore, in the above-mentioned control systems, operation of the electric motor is stopped in order to prevent damage.
However, stopping operation of a vehicle door control system when no actual possibility of damage exists is undesirable, as delays or complete shutdown prevent the use of the vehicle door and in public transportation applications, prevent persons from entering or exiting the vehicle.
Therefore, it would be desirable to provide a vehicle door control system and method whereby operation of the vehicle door may be continued after detection of an abnormality if a determination is made that the vehicle door control mechanism may be damaged or broken, while preventing operation that may cause damage to the vehicle door, door positioning mechanism or the electric motor.